PHD
  1. Inorganic chemistry  1.1. Coordination chemistry  1.1.1. Ligand field theory  1.1.2. Crystal field theory  1.1.3. Molecular Orbital Theory for Coordination Compounds  1.1.4. Stability of Coordination Compounds  1.1.5. Electronic spectra of coordination compounds  1.1.6. Isomerism in Coordination Compounds  1.1.7. Kinetics and mechanism of coordination reactions  1.2. Organometallic Chemistry  1.2.1. Metal Carbonyls  1.2.2. Metal alkyl and aryl  1.2.3. Fischer and Schrock carbonaceans  1.2.4. Oxidative Addition and Reductive Elimination  1.2.5. Metal Hydrides  1.2.6. Catalysis by organometallic compounds  1.2.7. Metallocenes and Sandwich Complexes  1.2.8. CH activation  1.3. Solid state chemistry  1.3.1. Crystal structures and lattices  1.3.2. Band theory and electrical properties  1.3.3. Defects in the crystal  1.3.4. Synthesis of solid state materials  1.3.5. Magnetic and optical properties of solids  1.3.6. Superconductivity  1.3.7. Solid state ionics  1.4. Bio-inorganic chemistry  1.4.1. Metalloproteins and enzymes  1.4.2. Metal ion transport and storage  1.4.3. The role of metals in medicine  1.4.4. Bioinspired catalysis  1.4.5. Metal–DNA interactions  1.4.6. Metal Complexes in Medical Science  1.5. Lanthanides and Actinides  1.5.1. Electronic configuration and oxidation states in lanthanides and actinides  1.5.2. Spectral and Magnetic Properties in Lanthanides and Actinides  1.5.3. Separation and Extraction of Lanthanides and Actinides  1.5.4. Coordination chemistry of f-block elements  1.6. Main Group Chemistry  1.6.1. Chemistry of boron compounds  1.6.2. Chemistry of Silicon and Germanium Compounds  1.6.3. Chemistry of Phosphorus and Sulfur Compounds  1.6.4. Organosilicon chemistry  1.6.5. Noble Gas Chemistry
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition and substitution reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic Reactions  2.1.7. Photochemical reactions  2.2. Stereoscopic  2.2.1. Chirality and optical activity  2.2.2. Structural analysis  2.2.3. Stereoelectronic effects  2.2.4. Asymmetric synthesis  2.2.5. Dynamic Stereochemistry  2.3. Organometallic Chemistry in Organic Synthesis  2.3.1. Organolithium and organomagnesium reagents  2.3.2. Transition metal catalyzed coupling reactions  2.3.3. Palladium-catalyzed reactions  2.3.4. Olefin Metathesis  2.3.5. Gold and silver catalysis  2.4. Natural products chemistry  2.4.1. Alkaloids and terpenoids  2.4.2. Steroids and Flavonoids  2.4.3. Total synthesis of natural products  2.4.4. Biosynthesis of natural products  2.5. Supramolecular Chemistry  2.5.1. Host-Guest Chemistry  2.5.2. Self-assembly and molecular recognition  2.5.3. Supramolecular Catalysis  2.5.4. Molecular Machines
  3. Physical Chemistry  3.1. Thermodynamics  3.1.1. Laws of Thermodynamics  3.1.2. Chemical Potential and Equilibrium  3.1.3. Statistical thermodynamics  3.1.4. Non-equilibrium thermodynamics  3.2. Quantum Chemistry  3.2.1. Schrödinger equation and its applications  3.2.2. Molecular orbital theory  3.2.3. Density functional theory  3.2.4. Post-Hartree–Fock methods  3.3. Chemical kinetics  3.3.1. Reaction rate theory  3.3.2. Mechanism and rate laws  3.3.3. Catalysis and enzyme kinetics  3.3.4. Reaction dynamics  3.4. Spectroscopy and molecular structure  3.4.1. Infrared Spectroscopy  3.4.2. UV-visible spectroscopy  3.4.3. Nuclear Magnetic Resonance Spectroscopy  3.4.4. Mass Spectrometry  3.4.5. Raman Spectroscopy  3.5. Surface and Colloid Chemistry  3.5.1. Absorption and Catalysis  3.5.2. Surfactants and micelles  3.5.3. Colloidal Stability  3.5.4. Nanomaterials and Interfaces
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.1.4. Ion Chromatography  4.2. Electroanalytical techniques  4.2.1. Voltammetry and Polarography  4.2.2. Conductometry and potentiometry  4.2.3. Colometry  4.3. Spectroscopic Methods  4.3.1. Atomic absorption spectroscopy  4.3.2. Fluorescence Spectroscopy  4.3.3. X-ray diffraction  4.3.4. Electron paramagnetic resonance spectroscopy  4.4. Chemometrics  4.4.1. Data processing and statistical methods  4.4.2. Multidisciplinary analysis  4.4.3. Machine Learning in Analytical Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.2. Quantum chemistry methods  5.3. Computational drug design  5.4. Machine Learning in Chemistry  5.5. Ab initio molecular dynamics
  6. Biophysics and Medicinal Chemistry  6.1. Drug discovery and design  6.2. Enzyme kinetics and inhibition  6.3. Chemical biology approach  6.4. Protein-ligand interactions  6.5. Bioorthogonal chemistry
  7. Materials chemistry  7.1. Polymer chemistry  7.1.1. Polymerization mechanism  7.1.2. Functional Polymers  7.1.3. Biodegradable Polymer  7.1.4. Conducting and semiconducting polymers  7.2. Nano Chemistry  7.2.1. Nanoparticles and nanostructures  7.2.2. Carbon-based nanomaterials  7.2.3. Quantum dots  7.3. Energy and Environmental Chemistry  7.3.1. Battery and Fuel Cell Chemistry  7.3.2. Green chemistry and sustainable materials  7.3.3. Photocatalysis

PHD → Inorganic chemistry → Coordination chemistry ↓


Isomerism in Coordination Compounds


Isomerism is a fascinating concept in coordination chemistry, which highlights how the structure or arrangement of atoms can differ in compounds having the same chemical formula. Such differences can lead to different physical and chemical properties. Understanding the types of isomerism in coordination compounds is essential for understanding their reactivity and their applications in various fields, such as catalysis and materials science. In this article, we will learn in detail about the different types of isomerism found in coordination compounds.

Types of isomerism

Isomerism in coordination compounds is generally classified into two main categories: structural isomerism and stereoisomerism. Each category is further divided into subtypes, which we will look at in detail.

Structural isomerism

Structural isomerism arises when the valency of atoms within isomers differs. There are several types under this category:

1. Coordination isomerism

Coordination isomerism occurs when the structure of the complex ion changes. This type is usually found in compounds where both the cation and anion are complex ions. Consider the coordination compounds [Co(NH3)6][Cr(CN)6] and [Cr(NH3)6][Co(CN)6]. Here, the ligand has switched positions between the cationic and anionic complexes, giving rise to coordination isomerism.

2. Ionization isomerism

Ionization isomerism arises when the anti ion in a coordination compound can also bind directly to the central metal atom as a ligand. As a result, different ionic species are formed in solution. For example, consider the compounds [Co(NH3)5Br]SO4 and [Co(NH3)5SO4]Br. Each compound gives a different ion when dissolved in water, thus representing ionization isomerism.

3. Linkage isomerism

Linkage isomerism occurs when a ligand can attach to the central atom through multiple bonds, forming isomers. A common example is the ligand NO2-, which can attach through either nitrogen or oxygen, forming [Co(NO2)(NH3)5]2+ and [Co(ONO)(NH3)5]2+. These are linkage isomers of each other.

4. Hydrate isomerism

Hydrate isomerism or solvate isomerism occurs when water molecules can be either in the coordination sphere or free in the crystal lattice. A classic example is [Cr(H2O)6]Cl3 which loses water to [Cr(H2O)5Cl]Cl2.H2O and [Cr(H2O)4Cl2]Cl.2H2O

5. Coordination position isomerism

Coordination position isomerism occurs in compounds that differ in the position of the ligands around the central metal atom but contain the same group of atoms. It is less common than other types of isomerism but is important in understanding catalytic and physical properties.

Stereoisomerism

Stereoisomerism involves compounds in which the valency of atoms is the same but the spatial arrangement of these atoms is different. This category is further divided into two primary types:

1. Geometrical isomerism

Geometric isomers differ in the spatial arrangement of the ligands around the central atom, usually in square planar and octahedral complexes. A good example of this is [Pt(NH3)2Cl2], which can exist as a cis or trans isomer:

SisPtChlorineChlorineNH3NH3TransPtChlorineNH3ChlorineNH3

In the cis isomer the similar ligands are adjacent, while in the trans isomer they are opposite to each other.

2. Optical isomerism

Optical isomerism arises when compounds exist as non-superimposable mirror images, often called enantiomers. This property is important in fields such as pharmacology, where different enantiomers may have different biological activities.

Tetrahedral complexes with mixed ligands and specific octahedral complexes such as [Co(en)3]3+ exhibit this type of isomerism. Here, the mirror images rotate plane-polarized light in different directions as shown:

[no(en)3]3+mirror[no(en)3]3+

Optical activity evaluation is important in understanding the properties that differentiate these isomers in their respective interactions.

Summary

In conclusion, isomerism in coordination compounds is a vast and compelling topic, emphasizing the complexity and diversity of chemical structures. It is important for anyone involved in advanced inorganic chemistry to appreciate these differences. Whether it is the color changes observed due to different coordinations or the unique behaviors in biological systems, isomerism plays a vital role in shaping the function and application of coordination compounds.

This exploration of isomerism only scratches the surface of what coordination chemistry has to offer to academia and industry. The continued study of these complex phenomena enriches our understanding of chemistry and materials science, paving the way for new discoveries and innovations.


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Isomerism in Coordination Compounds

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